Under sanctions imposed by the U.S. and its allies, dollars are hard to come by in Iran. The rial fell from 20,160 against the greenback on the street market in August to 36,500 rials to the dollar in October. It’s settled, for now, around 27,000. The central bank’s fixed official rate is 12,260. Yet there’s one currency in Iran that has kept its value and can be used to purchase goods from abroad: bitcoins, the online-only currency.